how to define global variable in javascript

Question

I am wondering how I can define a global variable in javascript. That's what I am doing and I want currentValue to be global so everytime gotoNext and previous function can change its value

onPageClick : function(event) { var currentValue = event.target.innerHTML; if (currentValue == "Next") this.gotoNext(); if (currentValue == "previous") this.gotoPrev(); }, gotoNext : function() { this.currentValue +1; }, gotoPrevious : function() { this.currentValue -1; },

but currentValue is not defined in goToNext and gotoPrevious!

possible duplicate of Using a global variable in javascript

NDM
– NDM

2013-09-19 07:22:05 +00:00
Commented Sep 19, 2013 at 7:22 — NDM
– NDM, Commented Sep 19, 2013 at 7:22

Evan Trimboli · Accepted Answer · 2013-09-19 07:12:21Z

3

You're not really asking about a global variable, but a class level variable.

You need to set this.currentValue = event.target.innerHTML;

answered Sep 19, 2013 at 7:12

Evan Trimboli

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2 Comments

user2781855 Over a year ago

and where should I declare it? outside of function?

Evan Trimboli Over a year ago

You don't need to declare it. Just setting this.foo = 1; is enough.

Scalpweb · Accepted Answer · 2013-09-19 07:17:45Z

You need to define currentValue outside of any function scope. Like this:

<script> var currentValue = ''; /* YOUR SCRIPT GOES HERE */ </script>

But then, you must change your code on the two last functions:

gotoNext : function() { currentValue += 1; }, gotoPrevious : function() { currentValue -= 1; }

But be carefull with this, globale variables are a bad thing. IMO, the best way to define an object is as follow:

var yourObject = function(){ var currentValue = ''; var that = { onPageClick : function(event) { var currentValue = event.target.innerHTML; if (currentValue == "Next") that.gotoNext(); if (currentValue == "previous") that.gotoPrevious(); }, gotoNext : function() { currentValue += 1; }, gotoPrevious : function() { currentValue -= 1; } }; return that; };

And then, you use it like this:

var obj = yourObject(); obj.gotoNext(); obj.gotoPrevious();

I would advise you to learn about scope and closures :

http://robertnyman.com/2008/10/09/explaining-javascript-scope-and-closures/

Thanks you so much, actually there is an event: events : {"click a.a-page-item" : "onPageClick"}, when you click obPaecick function get called. but if I define it inside var yourObject = function(){ it deos not get called.
Could you please create a FiddleJS with your code, so I can help you ? Thx

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